The undesired destruction of healthy cells by the immune system results in the loss of tissue function and complicates strategies to restore tissue function. The current standard therapy for autoimmune disease involves generalized immunosuppression, which is in most cases is not clinically efficacious and leads to numerous undesired side effects. Dr. Stephen Miller, (co-PI) pioneered an approach in which splenocytes were crosslinked with specific autoantigens, and their delivery to the spleen induced tolerance specifically to the autoantigen. The use of cellular carriers for tolerance induction in the clinical arena is challenging due to the considerable ex-vivo laboratory manipulation that is required, which is expensive, increases the number of donor cells needed and introduces further opportunity for technical error. Our long-term goal is to develop a particle-based platform that can be an off-the-shelf product for induction of tolerance to specific antigens to inhibit the specific undesired immune response while not altering the remaining elements of the immune response. In this proposal, we develop particles that target the spleen following intravenous delivery, and would subsequently be internalized by 'tolerogenic' antigen presenting cells to present the antigens without T cell activation thereby inducing tolerance rather than an immune response. Most strategies targeting the immune system focus on inducing a specific immune response (vaccines), whereas this system aims to do the opposite by inducing tolerance to specific antigens. We hypothesize that peptide-linked particles will be internalized by tolerogenic host splendid APCs which subsequently induce immune tolerance through the coordinate induction of T cell energy and activation of regulatory T cells that limit T cell responses. We have selected biocompatible and biodegradable materials whose physical properties can be controlled to influence their distribution, and can be modified with functional groups to promote internalization, target specific APC populations or receptors, and can release bioactive proteins to enhance the tolerogenic response. The following aims will be investigated: Specific Aim 1 will investigate particle design for splenic homing and antigen presentation in tolerance induction. Specific Aim 2 will investigate the innate cellular mechanisms that mediate interactions with antigen-linked particles that lead to tolerance. Specific Aim 3 will investigate mechanisms of particle-initiated inactivation of effectors T cell functions mediating tolerance induction including clonal deletion, energy/immune deviation, and Treg activation. Successful completion of these studies would identify particles that are novel, safe, efficient and clinically relevant tools to inhibit antigen-specific T- cells for therapy of autoimmune diseases. This innovative approach has far reaching implications for applications in which decreasing specific immune responses could be beneficial, such as the autoimmune diseases, rejection of transplanted cells, and allergies to food antigens or airborne particulates.